The present invention relates generally to antennas, and more particularly to patch antennas.
Design parameters of antennas are determined by the application of interest. Weakly-directional antennas are advantageous for many applications, such as global navigation satellite systems (GNSSs). Well-known examples of GNSSs include the United States Global Positioning System (GPS) and the Russian GLONASS system. Other systems, such as the European Galileo system, are planned. Proprietary systems such as the OmniSTAR differential GPS have also been deployed.
In a GNSS, a navigation receiver tracks radiofrequency signals transmitted by a constellation of satellites. Accuracy in determining the position of the navigation receiver increases as the number of satellites tracked by the navigation receiver increases. The receiving antenna, therefore, should have a uniform radiation pattern in the forward hemisphere.
The number of satellites tracked by a navigation receiver can also be increased if the navigation receiver is capable of tracking signals from more than one GNSS. A multi-system navigation receiver, for example, can track signals from GPS, GLONASS, and Galileo satellites. For multi-system operation, a receiving antenna with a wide bandwidth is needed.
Many GNSS applications require mobile receivers that are compact and lightweight. Since the receiving antenna is typically integrated with the navigation receiver, the receiving antenna also needs to be compact and lightweight.
Antennas with compact size, light weight, uniform radiation pattern in the forward hemisphere, and wide bandwidth are therefore desirable.